Locking device

ABSTRACT

A pressure-sensitive locking device comprises a housing ( 2,20 ) having an opening therein, and an insertable member ( 1,21 ) adapted to be inserted into the opening whereupon it can enter into locking engagement with a locking member ( 4,36 ) in the housing. The locking member ( 4,36 ) is cooperable with pressure-sensitive means ( 7,28 ) in the housing to effect disengagement between the locking member ( 4,36 ) and the insertable member ( 1,21 ) upon a reduction of pressure.

[0001] This invention relates to a locking device, and more particularlyto a locking device which is automatically engageable or disengageableupon a change in pressure.

[0002] A particular application for such a locking device is as asecurity seal for use on passenger aircraft. The device can be used toseal the containers used for the in-flight distribution of perishableand non-perishable goods. The theft of goods from containers costsairlines vast sums of money each year. Although containers are sealedwhen they leave the warehouse, it is necessary for the seals to beeasily removable by hand as it is quite impractical for cabin crews tocarry special seal removal tools on the aircraft. We have found thatthese problems can be solved by a locking device which ispressure-sensitive, the device thus being actuated by the reducedpressure during flight.

[0003] The present invention thus provides a pressure-sensitive lockingdevice comprising a housing having an opening therein, an insertablemember adapted to be inserted into the housing through the opening, anda locking member in the housing, the locking member being biased towardsengagement with the insertable member so that the locking member islockably engageable with the insertable member upon insertion of theinsertable member into the housing, and the locking member beingcooperable with pressure-sensitive means in the housing to effectdisengagement of the locking member from the insertable member upon areduction of pressure.

[0004] In a preferred embodiment, the locking member is resilientlybiased towards the insertable member when inserted in the housing so asto be in locking engagement therewith under normal atmospheric pressure.When the pressure is reduced, for example when an aircraft achieves apredetermined altitude, the pressure-sensitive means effectsdisengagement of the locking member from the insertable member,whereupon the insertable member can be withdrawn from the housing.

[0005] The opening in the housing preferably communicates with achannel, and the insertable member is preferably elongate and adapted tobe slidingly inserted lengthwise through the opening into the channel.

[0006] The locking device can serve both as a barrier seal and as anindicative seal. The elongate member can be shaped so as to engage witha hasp or other securing device of an aircraft goods container.Alternatively, the elongate member can be U or J-shaped whereby thelimbs can be inserted in two channels in the housing and lockable in oneor both such channels, the device then being usable in the same way as apadlock. The locking device preferably includes an additional disposablelocking element which engages with the elongate member in the lockedposition, and which has to be physically broken to permit withdrawal ofthe elongate member from the channel.

[0007] Reference is now made to the accompanying drawings, in which:

[0008]FIG. 1 is a diagrammatic representation, partly in cross-section,of a locking device according to a first embodiment of the invention,the device being shown in the locked condition;

[0009]FIG. 2 is a view corresponding to FIG. 1 but with the deviceunlocked;

[0010]FIG. 3 is an exploded perspective view of a locking deviceaccording to a second embodiment of the invention;

[0011]FIG. 4 is an end view of a disposable locking element used in thesecond embodiment;

[0012]FIG. 5 is a plan view of the second embodiment when ready to belocked;

[0013]FIG. 6 is a plan view of the second embodiment in the lockedposition, and partly cutaway to show internal details;

[0014]FIG. 7 is a plan view of a combined capsule and locking memberused in the second embodiment;

[0015]FIG. 8 is a side view corresponding to FIG. 7;

[0016]FIG. 9 is a partial end view corresponding to FIGS. 7 and 8;

[0017]FIG. 10 is a part-sectional side view showing the operation of thecombined capsule and locking member of the second embodiment in thelocked condition;

[0018]FIG. 11 corresponds to FIG. 10 and shows the device unlocked by areduction in air pressure;

[0019]FIG. 12 corresponds to FIGS. 10 and 11 and shows the operation ofa secondary locking member to prevent unauthorised or accidental “shock”opening;

[0020]FIGS. 13 and 14 are diagrammatic plan views showing a modificationof the second embodiment; and

[0021]FIGS. 15 and 16 are sectional views corresponding respectively toFIGS. 13 and 14.

[0022] Referring first to FIGS. 1 and 2, there is shown a housing 2 witha channel 9 defined therein. An elongate member in the form of a bar 1of cylindrical section is able to slide within the channel. The bar 1has a tapered head and immediately behind this a groove 3. A lockingmember 4 is provided within the housing and is rotatable about an axis10. One end of the locking member has an enlarged head shaped so as toengage with the groove 3 of the bar 1. An opposite end of the lockingmember 4 is engaged with one end of a helical spring 8, the other end ofwhich is mounted in the housing 2. The spring 8 resiliently biases thelocking member 4 into locking engagement with the groove 3 of the bar 1.When the bar 1 is initially inserted into the channel 9, the taperedhead of the bar slides past a sloping surface of the head of the lockingmember 4, thereby deflecting the locking member against its spring bias,and then the locking member snaps into engagement with the groove 3. Thelocking engagement between the locking member 4 and the groove 3prevents withdrawal of the bar 1 from the channel 9.

[0023] Also provided within the housing is a pressure-sensitive means inthe form of a capsule 7 which communicates with a tube 6 but isotherwise air-tight. The capsule 7 has concertina-like flexible sidewalls to permit expansion and contraction. An elongated sliding elementS with rounded ends is provided in a transverse channel 11 which adjoinsthe channel 9. Before insertion of the bar 1, one end of the slidingelement 11 projects slightly into the channel 9. As the bar 1 isinserted, it deflects the sliding element 5 to one side so that itslides further into the transverse channel 11. This causes the oppositeend of the sliding element 5 to press against the side of the tube 6,which is of flexible material. The tube 6 is thereby sealed at thispoint, with the result that the capsule 7 is completely air-tight.

[0024] As the pressure is reduced, for example, as an aircraft increasesaltitude, the pressure of the air enclosed within the capsule 7 becomesgreater than that of the surrounding air, with the result that thecapsule expands, as shown in FIG. 2. An end of the capsule 7 abutsagainst a rounded contact point on the locking piece 4, intermediate theaxis 10 and contact point of the spring 8. Expansion of the capsule 7,as shown in FIG. 2, thus causes the locking piece 4 to pivot about theaxis 10, whereby the head of the locking piece 4 becomes disengaged fromthe groove 3 in the bar 1. The bar 1 can then be freely withdrawn fromthe channel 9. Once the bar 1 has been withdrawn, the sliding element 5ceases to be pressed against the tube 6, and the natural resilience ofthe tube 6 pushes the sliding element 5 back towards the channel 9. Aircan therefore pass from within the capsule 7 and out through the tube 6,thereby equalising the pressures inside and outside the capsule 7. Thespring 8 will then cause pivoting of the locking piece 4 about the axis10, so that the head of the locking piece 4 once more projects into thechannel 9. If the bar 1 is then reinserted into the channel 9, it willagain engage with the head of the locking piece 4 to effect locking.Once this position has been reached, and without any further reductionin pressure, unlocking of the device can only be achieved by destructionof parts thereof, for example by cutting the bar 1. If desired, aspecial tool could be designed to disengage the locking piece 4 from thebar 1, although such an arrangement would be inherently less secure.

[0025] The locking device described above is typically used to seal agoods container, for example a drinks trolley, for use on an aircraft.The trolley is filled at the warehouse and then locked with the lockingdevice. If the trolley is to be inspected by authorised personnel whilestill on the ground, the locking device is opened by cutting the bar,and the trolley is then locked with a new locking device. The lockingdevice can thus only be opened on the ground by destroying at least partof it, and thus any interference with the trolley is readily apparent toan inspector. Once on the aircraft, above a designated altitude, thelocking device is automatically unlocked by the reduced pressure. Thetrolley can then be used in the normal way, and after use it can berelocked with the same locking device. Thereafter, the locking devicecan again only be unlocked by destruction of at least part of it, whichwould be done by authorised personnel. Again, any unauthorisedinterference would be readily apparent to an inspector.

[0026] Referring now to FIGS. 3 to 12, a second embodiment of theinvention is described. The locking device shown includes a housing 20,an insertable member in the form of a flat bar 21 and a disposablelocking element 22. The housing has a hinged guide member 23, pivoted toan end portion 24 of the housing. The guide member 23 is able to pivotbetween an open position (FIG. 5) and a closed position (FIG. 6). Theguide member 23 has an opening 25 for receiving the bar 21, and in theclosed position the opening 25, which extends through the guide member,is in register with openings at opposing ends of the main body of thehousing 20, so as to effectively form a channel through the housing.

[0027] The bar 21 is J-shaped. An end portion of the longer limb can bepre-placed in the opening 25 of the guide member 23, with the guidemember in the open position as shown in FIG. 5. In order to effectlocking, as described in more detail below, the guide member 23 is thenrotated to the closed position (FIG. 6) and the longer limb of the bar21 is then fully inserted in the channel of the housing 20, the endportion of the longer limb projecting slightly from the other side ofthe housing (FIG. 6). The shorter limb of the bar 21 is received in anopening 26 in a side wall of the housing, and in the locked positiontravels to a short extent through the opening into the interior of thehousing (FIG. 6). The fit of the end of the longer limb of the bar 21 inthe opening 25 is sufficiently close that the bar 21 can be held by theguide member 23, as shown in FIG. 5, but does not impede furtherinsertion of the bar 21 through the opening 25 until the bar reaches thelocked position, as shown in FIG. 6.

[0028] Inside the housing 20 is a locking member 27 which incorporates apressure-sensitive device in the form of a sealed capsule 28. Thecapsule 28 is in the form of a shallow cylindrical cup, one end of whichis sealed by an elastomeric membrane 29. The cup and the membrane definea closed space. A short extension piece 30 to one side of the capsuleterminates in a transverse hinge member 31 which cooperates with a hingesupport 32 inside and at one end of the housing 20. Extending from theopposite side of the capsule 28, but slightly offset from the extensionpiece 30, is an arm 33. On the underside of the arm, close to thecapsule 28, there is formed a cylindrical cup 34 for receiving an end ofa helical spring 35, the other end of the spring being mounted on aninternal wall of the housing. By virtue of the hinge 31 and the spring35, the arm 33 of the locking member is biased away from the internalwall of the housing on which the spring 35 is mounted. Also on theunderside of the arm 33, but closer to its free end, there is anintegral locking piece 36 in the form of a ridge having a sloping ramp37 at one side (FIG. 9).

[0029] The bar 21 has a rectangular slot 38 towards the end of itslonger limb. As the bar 21 is inserted into the housing, the leadingedge of its longer limb passes under the arm 33 of the locking member.The leading edge first strikes the ramp 37 of the locking piece 36, andrides up the ramp, thereby pressing the arm 33 against the bias of thespring 35. On further insertion, the locking piece 36 becomes level withthe slot 38 in the bar 21, and at this point the spring 35 causes thearm 33 with its integral locking piece 36 to snap into engagement withthe slot 38. Attempted withdrawal of the bar 21 is prevented byengagement between the end of the locking piece 36, opposite to the ramp37, with the trailing end (on extraction) of the slot 38.

[0030] In this position, the bar 21 is securely locked in the housing20. With this arrangement, there is a risk that a sharp blow to one sideof the housing, closest to the underside of the arm 33, couldmomentarily deflect the arm against the spring 35, which would permitthe bar 21 to be withdrawn (referred to herein as “shock opening”). Sucha blow could be inflicted deliberately in an attempt to interfere withthe locking device, or by accident. In order to overcome this problem,there is provided a secondary locking member 39 (FIGS. 10 to 12). Thesecondary locking member 39 is shaped similarly to the locking member 27except that it does not have the capsule 28. The secondary lockingmember 39 has at one end a hinge member 40 which is mounted inside thehousing close to the hinge member 31 of the locking member 27. Close toits opposite end, there is an integral upstanding locking piece 41,similar to the locking piece 36 but without a ramp. As shown in FIG. 10,the secondary locking member 39 normally lies alongside an internal wallof the housing, with the locking piece 41 close to but not actuallyengaged with the slot 38 of the bar 21. In this position, if a sharpblow is applied to the housing wall adjacent the secondary lockingmember, the locking member 27 may be momentarily deflected out ofengagement with the slot 38, as shown in FIG. 12. However, such a blowwill deflect the secondary locking member 39 in the same direction, andthis will be into locking engagement between the locking piece 41 andthe slot 38. The slot 38 is designed to be sufficiently wide that bothlocking pieces 36 and 41, which are offset from each other, can beaccommodated. When the effect of the sharp blow has subsided, the spring35 returns the locking member 27 and locking piece 36 into engagementwith the slot 38 of the bar 21, and the arrangement is again as shown inFIG. 10.

[0031] When the locking device is in the locked position (FIG. 10) apredetermined reduction in ambient pressure will cause it to beunlocked. When the ambient pressure is reduced, the pressure of the airenclosed in the sealed capsule 27 causes the elastomeric membrane 29 toexpand outwardly. This membrane abuts against the surface of thesecondary locking member 39, which in turn abuts against the internalsurface of the housing. The result is that the locking member 27, byvirtue of its hinge 31, is pressed against the bias of the spring 35,and the locking piece 36 is raised out of engagement with the slot 38,as shown in FIG. 11. The locking device is then unlocked, and the bar 21can be withdrawn. The elastomeric grade of the membrane 29 can beadapted to provide locking devices which will be unlocked over a rangeof predetermined pressure changes.

[0032] The locking device includes a supplementary security seal in theform of a disposable locking element 22 (FIGS. 3 and 4). The disposablelocking element 22 includes a head part 42 in the form of a flat tab,and upstanding on one side thereof a plug part 43 and a locking post 44.The disposable locking element 22 cooperates with the guide member 23(which is part of the housing 20) and the bar 21 in the followingmanner.

[0033] The bar 21 has a circular hole 45 in its longer limb spaced fromthe trailing end (on insertion) of the slot 38. The guide member 23 hasa corresponding through hole 46 whereby, when the bar 21 is locked inthe housing 20, the holes 45 and 46 are in register and can receive thelocking post 44 of the disposable locking element 22. The guide member23 has a hollow interior, with an opening 47 spaced to one side of thehole 46. The plug part 43 of the disposable locking element is in theform of a resilient barb. The plug part 43 passes through the opening 47as the locking post 44 is inserted through the holes 46 and 45. As theplug part 43 passes through the opening 47, the barb is resilientlydeflected to one side, but as soon as it is inside the guide member 23,the barb resiliently returns to its original dimensions, and resistswithdrawal. In this position, the bar 21, as well as being locked by thelocking member 27 inside the housing, is additionally locked by thelocking post 44. Thus, even when a reduction in pressure has caused thelocking member 27 to disengage from the bar 21, the disposable lockingelement 22 must additionally be released in order to withdraw the bar21.

[0034] The head part 42 incorporates a tear line which separates theparts of the head part respectively attached to the plug part 43 and thelocking post 44. Thus, by manual manipulation, which is assisted by apull tab 48, the disposable locking element can be split into two parts.The locking post 44 can then be freely withdrawn, permitting release ofthe bar 21. The plug part 43 remains inside the guide member 23 but theguide member 23 can now be freely rotated to the open position, therebyreleasing the plug part. The disposable locking element 22 can be markedfor security purposes, such as with a serial number or bar code. Ifdesired, the locking device can be relocked using a new disposablelocking element.

[0035] FIGS. 13 to 16 illustrate a modification of the second embodimentof the invention (FIGS. 3 to 12). Instead of the secondary lockingmember 39 (which is absent in FIGS. 13 to 16), shock opening isprevented by modifying an internal chamber 49 in the housing andallowing a loose fit of the hinge 31. The loose fit permits a smallamount of sideways movement of the arm 33, whereby the bar 21 can bepushed slightly beyond its normal locking position (FIGS. 13 and 15) toan extended position (FIGS. 14 and 16). The effect of this can be seenby comparing FIG. 15, which is a section on the line XV-XV of FIG. 13,with FIG. 16, which is a similar section corresponding to FIG. 14. Thechamber 49 is provided with a step 50 near the point of entry of the bar21. The step 50 is dimensioned such that the thickness of the arm 33 canjust fit between the step 50 and the bar 21. Thus, in the normal lockingposition shown in FIGS. 13 and 15, the step 50 prevents shock opening.Shock opening can only be achieved if the bar 21 is pulled away from thehousing simultaneously with applying the shock, and in this position thestep 50 prevents movement of the arm 33 to take the locking piece 36 outof engagement with the bar 21.

[0036] When a fall in pressure permits normal opening (in the manneralready described), the disposable locking element 22 is firstextracted. The bar 21 can then be pushed into the extended position(FIGS. 14 and 16), where the holes 45 and 46 are now slightly out ofregister. The arm 33 is now moved off the step 50. The spring 35 willcause it to remain in engagement with the bar 21 (as shown in FIGS. 14and 16). However, if the pressure has fallen sufficiently, the expansionof the capsule 28 will cause the arm 33 to move out of engagement withthe bar 21. The bar 21 can then be pulled out of the housing asdescribed above.

[0037] There may be a need to inspect a container locked by the lockingdevice while still on the ground. In this case, an authorised officialwill break the disposable locking element 22 and cut the bar 21 in itslonger limb, on the trailing side (relative to insertion) of the hole45. The leading end of the longer limb, which projects from the otherside of the housing, can then be pulled, and the residual part of thebar 21 withdrawn from the housing. This is possible because the ramp 37of the locking piece 36 will cooperate with the trailing end of the slot38, whereby the locking member 27 is moved out of engagement with theresidual part of the bar 21. The device is then relocked with a new bar21 and new disposable locking element 22.

[0038] It is sometimes desirable for containers on aircraft to beopenable while the aircraft is still on the ground, for example if thereis a flight delay. This can be accommodated according to the presentinvention by modifying some locking devices so that the slot 38 isabsent in the bar 21. The device is then not locked by thepressure-sensitive locking member 27, but is only locked by thedisposable locking element 22. In a typical situation, a limited numberof containers of the aircraft would be locked in this way, the remainingcontainers being locked in the full pressure-sensitive manner asdescribed above.

[0039] A container on an aircraft may be locked by the device accordingto the invention by cooperation between the bar 21 and a hasp or othersecuring device on the container. Alternatively, a cable may be providedwith loops at its end. The cable is then used to secure a container doorin the closed position and the loops are held by the bar 21 which actsin the manner of a padlock.

1. A pressure-sensitive locking device comprising a housing having anopening therein, an insertable member adapted to be inserted into thehousing through the opening, and a locking member in the housing, thelocking member being biased towards engagement with the insertablemember so that the locking member is lockably engageable with theinsertable member upon insertion of the insertable member into thehousing, and the locking member being cooperable with pressure-sensitivemeans in the housing to effect disengagement of the locking member fromthe insertable member upon a reduction of pressure.
 2. A locking deviceaccording to claim 1, in which the opening communicates with a channelin the housing, and the insertable member is elongate and adapted to beslidingly inserted lengthwise through the opening into the channel.
 3. Alocking device according to claim 1 or 2, in which the locking member ispivotable.
 4. A locking device according to any of claims 1 to 3, inwhich the pressure-sensitive means comprises an expandable sealedcapsule in abutment with a surface of the locking member, wherebyexpansion of the capsule causes movement of the locking member out ofengagement with the insertable member.
 5. A locking device according toclaim 4, including means to permit air to flow freely in or out of thecapsule when the insertable member is totally or partially withdrawnfrom the housing.
 6. A locking device according to any of claims 1 to 3,in which the pressure-sensitive means comprises a sealed capsuleincorporated in the locking member, the capsule having an expandablesurface in abutment with a surface in the housing, whereby a reductionin pressure causes expansion of the expandable surface and consequentmovement of the locking member out of engagement with the insertablemember.
 7. A locking device according to any of claims 1 to 6, includinga secondary locking member adapted to lockably engage with theinsertable member when an applied shock displaces the locking member outof engagement with the insertable member.
 8. A locking device accordingto any of claims 1 to 6, wherein a step inside the housing is inabutment with the locking member so as to prevent the locking memberbecoming disengaged from the insertable member on application of ashock, and wherein further insertion of the insertable member into thehousing moves the locking member out of abutment with the step,whereupon disengagement of the locking member from the insertable memberbecomes possible.
 9. A locking device according to any of claims 1 to 8,further including a disposable locking element adapted to engage withthe insertable member and/or the housing when the insertable member isin locking engagement with the locking member, whereupon breakage ofpart of the disposable locking element permits disengagement thereoffrom the insertable member and/or from the housing.
 10. A locking deviceaccording to claim 9, in which the disposable locking element is adaptedto lockably engage with the insertable member and/or the housing,whereby withdrawal of the insertable member from the housing isprevented even when the locking member is disengaged from the insertablemember.
 11. A locking device according to claim 9 or 10, in which thedisposable locking element is of plastics material and includes a headpart and a plug part, the plug part being resiliently deformable so asto permit engagement with but resist disengagement from the housingand/or the insertable member, and the head part including a tear linewhereby manual manipulation of the head part will permit separationthereof from the plug part with resultant disengagement from the housingand/or the insertable member.